[guardian-dev] Dm-verity

Matej Kovacic matej.kovacic at owca.info
Thu May 29 04:58:34 EDT 2014


Hi,

Android 4.4 introduced a security feature called verified boot.

This experimental feature helps Android users be sure when booting a
device it is in the same state as when it was last used.

Verified boot is solving the problem of malware with root privileges,
which can hide from detection programs and otherwise mask themselves.

The dm-verity feature lets you look at a block device, the underlying
storage layer of the file system, and determine if it matches its
expected configuration.

In more detail it is described here:
http://nelenkov.blogspot.com/2014/05/using-kitkat-verified-boot.html

Is that tool useful for preventing Evil Maid Attack? With Evil Maid
Attack it is possible to install a rootkit on the system partition of a
mobile phone, this rootkit could be automatically loaded via special
tailored (evil) mobile USB charger.

My question is, what are security deficiencies of such a tool?

One could be, that when a dm-verity device is configured, it is expected
that the caller has been authenticated in some way.

Another is some tampering with the bootloader. Anything else?

Regards,

M.


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